Chronic shoulder pain explained.

What causes chronic shoulder pain?

Most chronic shoulder pain starts with something identifiable — an overload, an awkward lift, a period of unusual activity, or a gradual onset with no clear trigger at all. What keeps it going for months is usually a different question from what started it.

Rotator cuff–related shoulder pain

The most common category, covering tendinopathy, partial tears, and what used to be called impingement. Pain is typically felt over the outer upper arm, worse with overhead reaching and with lying on that side at night. Terminology has shifted deliberately toward rotator cuff–related shoulder pain, because the older labels implied a mechanical pinching model that the evidence has not supported.

Frozen shoulder (adhesive capsulitis)

A distinct condition in which the joint capsule thickens and contracts, producing genuine restriction — most characteristically a loss of external rotation that is present whether you move the arm yourself or someone else moves it for you. It is more common in people with diabetes and thyroid disease, and it typically runs through painful, stiff, and thawing phases over one to three years.

Glenohumeral osteoarthritis

Less common in the shoulder than in the knee or hip, and as elsewhere, radiographic severity correlates poorly with symptoms.

Referred and neck-related pain

The neck refers pain into the shoulder region often enough that it should always be assessed. See chronic neck and shoulder pain.

Sensitization and guarding

This is the one most likely to be missed. After months of pain, the nervous system may amplify signals from the region, and the shoulder is held in a protective pattern that itself becomes painful. At this point the pain has less to do with the original tissue problem than with central sensitization and fear of movement.

Why doesn't the MRI explain the pain?

Because shoulder imaging is remarkably good at finding things that were never causing symptoms. Studies scanning people without any shoulder pain find rotator cuff tears at high rates, rising steeply with age — by the seventh and eighth decades, a substantial fraction of entirely pain-free shoulders have a tear.

This does not make imaging useless. It makes it a source of findings that need interpretation rather than answers that stand alone. A tear may be relevant, incidental, or somewhere in between, and only the clinical picture can settle which.

The unintended consequence is well documented: alarming imaging language increases fear, fear increases guarding, and guarding reduces the movement that would help. The scan can become part of the problem it was meant to explain.

Why does shoulder range of motion shrink — and what can restore it?

Outside of true frozen shoulder, most restriction in long-standing shoulder pain is not a mechanical block. It is the point at which the movement is expected to hurt. That distinction is testable, and it matters enormously for treatment.

Karuna Labs ran a small institutional review board–approved mechanistic study in 17 adults with chronic shoulder pain, using virtual reality to test how visual feedback affects pain-free range of motion. Participants moved their arms while a virtual avatar reflected the movement — sometimes matching the arm actually moving, sometimes displaying the movement of the healthy arm as though it were the painful one.

When people moved their unaffected arm but saw the painful side moving, pain-free range of motion significantly decreased for shoulder flexion and scaption. Nothing about the healthy arm had changed. What changed was which shoulder the brain believed was moving.

This was single-session mechanistic work in a small sample, not a demonstration of treatment benefit. What it supports is the principle: if perception can contract range of motion, then perception is a legitimate target for expanding it. That principle underpins mirror therapy, graded motor imagery, and our virtual reality training.

The shoulder is a particularly good fit for these approaches, because it is one of a pair. Mirror-based techniques that cannot help the lower back apply directly here.

How is chronic shoulder pain treated?

Exercise and graded loading

First-line in essentially every guideline, and the treatment with the most consistent support for rotator cuff–related shoulder pain. The principle is progressive loading within tolerance — enough to drive adaptation, not so much as to provoke repeated flares. Specific exercise programmes have performed comparably to surgery in trials.

Addressing fear and guarding

Where movement is limited by anticipated pain, graded exposure to the feared movements is the direct treatment. See kinesiophobia.

Injections

Corticosteroid injection can provide short-term relief and is sometimes used to create a window in which rehabilitation becomes possible. Benefits are generally short-lived, and injections work best as an adjunct to exercise rather than a replacement for it.

Surgery

The evidence here has shifted substantially. Placebo-controlled trials of subacromial decompression — including the CSAW and FIMPACT trials — found no meaningful benefit over sham surgery for subacromial shoulder pain. Surgery retains a clear role in specific situations: acute traumatic cuff tears in younger people, instability, and advanced arthritis. It is much less clearly indicated for long-standing non-traumatic shoulder pain.

Frozen shoulder specifically

Management differs. Pain relief and gentle range-of-motion work dominate the painful phase, with more assertive mobilisation as it settles. Hydrodilatation and corticosteroid injection are used, and most cases resolve over one to three years — though residual restriction is common.

When should you see a doctor about shoulder pain?

Most chronic shoulder pain is not dangerous. Some presentations need prompt assessment, and this list is not something to self-manage around.

• Significant trauma — a fall, dislocation, or sudden injury, particularly with deformity or inability to move the arm.
• Sudden loss of active movement while passive movement is preserved — this can indicate an acute rotator cuff tear.
• Fever, redness, heat, or swelling in the joint — possible infection, which requires urgent care.
• Unexplained weight loss, night sweats, or a history of cancer alongside new shoulder pain.
• Chest pain, jaw or left arm pain, breathlessness, or nausea — shoulder pain can refer from the heart. This is an emergency; call your local emergency number.
• Pain after abdominal surgery or injury, especially left-sided shoulder tip pain, which can indicate referred pain from the diaphragm.
• Numbness, weakness, or pins and needles spreading down the arm, suggesting nerve involvement.
• Progressive stiffness with loss of external rotation — worth assessing for frozen shoulder, especially with diabetes.